Process for preparing acetyl butadienes



United States Patent This application is a division of applicationSerial No.

93,857, filed March 7, 1961, now US. Patent No.

The present invention relates to butadiene iron subgroup metaltricarbonyl compounds, more particularly to the use of such compounds aswell as to products which are thereby made available. v

Among the objects of the present invention is the acylation of butadieneiron subgroup metal tricarbonyls.

Additional objects of the present invention include the provision ofnovel techniques for preparing chemical compounds, and novel compoundsthat can be so prepared.

The above as well as further objects of the present invention will bemore clearly understood from the following description which includesseveral exemplifications of the invention.

It has been discovered that butadiene iron subgroup metal tricarbonylscan be readily acylated in the presence of Friedel-Crafts catalysts togive good yields of acyl derivatives, and that these acyl derivativescan be readily split to recover an acyl butadiene, free of the metal andof the carbonyl groups present in the original starting material. Theabove iron subgroup metals are iron, ruthenium, and osmium. Thebutadiene portion of the butadiene iron subgroup metal tricarbonyls isthe conjugated form of butadiene but since this the the only formavailable in the above metallo tricarbonyls complex, no furtheridentification of the butadiene will be made.

The acylation of the present invention, and especially the good yieldsit provides, are quite unexpected inasmuch as Friedel-Crafts catalystsare known to cause decomposition of organometallic carbonyls as well asvigorous polymerization of butadiene, and also because extremely pooryields of acylated product are obtained when aliphatic hydrocarbons areacylated.

According to the present invention, butadiene iron subgroup metaltricarbonyls are simply and readily acyl ated in the presence ofFriedel-Crafts catalysts such as AlCl or other aluminum halides, ironhalides, or zinc halides. Other catalysts as well as the generalreaction conditions can be those conventionally used as described in Us.Patent 2,916,503, gnanted December 8, 1959, for instance. The reactionof the present invention can be carried out at room temperatures or atelevated or reduced temperatures with substantially no dilferences inthe yield.

The acylation causes the acyl group of the acylating agent to take theplace of one of the hydrogens of the butadiene portion of the molecule,and different isomers of the acylated product are formed in accordancewith the diiferent isomeric variations that are possible when differenthydrogens are thus substituted.

The following examples illustrate the present invention but do not limitit.

EXAMPLE 1 Acetylation of butadiene iron tricarbonyl The reaction wascarried out in a 1-liter 3-neck flask,

equipped with a condenser, a stirrer, a dropping funnel, a thermometerand a nitrogen inlet tube.

To 31.5 g. (.24 mole) of anhydrous aluminum chloride, slurried with 400ml. of cabron tetrachloride, there was added 14.6 g. (.20 mole) ofacetyl chloride. To this mixture there was added dropwise in a period of2.5 hours, 38.3 g. (.20 mole) of butadiene iron tricarbonyl diluted to150 ml. with carbon tetrachloride. A rapid stream of nitrogen was passedthrough the vigorously stirred solution throughout the addition. Thetemperature was kept within 3 degrees of 18 C. by controlling the rateof the dropwise addition. After it was completed, the mixture wasstirred for 20 minutes, then hydrolyzed with 300 ml. of water addeddropwise over 30 minutes, keeping the temperature below 20 C. The redcarbon tetrachloride layer which then separated was washed twice with 5%aqueous potassium carbonate solution, then twice with water. The waterlayers thus separated were combined and neutralized with solid sodiumcarbonate, thereby depositing a gelatinous material and the resultingslurry was extracted twice with carbon tetrachloride. The extracts werecombined with the washed carbon tetrachloride layer and this combinedsolution dried over magnesium sulfate overnight. The solvent was thenremoved by evaporation in vacuo. The remaining dark brown orangesolution was filtered and then distilled using. a short Vigreux column.Starting material (butadiene iron tricarbonyl) distilled at 2632 C. withthe pressure at 7.0l.2 mm. of Hg, giving 15.6 g. (41% recovery). Theproduct, acetylbutadiene iron tricharbonyl, was collected at 70-73 C.under a pressure of 0.2 mm. Hg. There was obtained 15.4 g. of product(55% yield based on consumed starting material). The product showed astrong absorption peak at 6.0 mu in the infrared, and gave a red2,4-dinitrophenylhydrazone melting with decomposition at 194 C. (afterrecrystallizing from ethyl acetate). The hydrazone derivative analyzedC43.7%, H3.04%, and Fe-13.3%, as against theoretical values (forC15H12FN407) Of and Fe-- 13.4%.

EXAMPLE 2 Benzoylation of butadiene iron tricarbonyl The apparatus ofExample 1 was used. To 33.4 g. (.25 mole) of anhydrous aluminumchloride, slurried with 400 ml. of carbon tetrachloride in the reactionflask, there was added 29.0 g. (.21 mole) of benzoyl chloride. Theaddition was accompanied by a temperature rise of 6 C. and someyellowing of the slurry. Then 40.0 g. (.21 mole) of butadiene irontricarbonyl, diluted to ml. with carbon tetrachloride, was addeddropwise over a period of 2.5 hours, keeping the temperature within 3de' grees of 12C. After the addition was completed, the reaction mixturewas stirred for two hours at l520 C., then hydrolyzed with 300 ml. ofwater, added dropwise over a period of 1.5 hours. Nitrogen was passedthrough the mixture continuously throughout-the addition, stirring andhydrolysis. The carbon tetrachloride layer was a then permitted tosettle, separated and washed three times with 5% aqueous potassiumcarbonate, then once with water. Each washing produced large amounts ofsolids at the interface. The combined water layers of the Washings wastreated with solid sodium carbonate until a color change (yellow to red)occurred, then was extracted twice with carbon tetrachloride. The maincarbon tetrachloride layer and the extracts were dried over magnesiumsulfate overnight, filtered and combined. The final solution wasconcentrated by evaporation in vacuo giving a dark brown, viscousliquid. This was diluted with diethylether and cooled in Dry Ice.Extended cooling and scratching produced some crystallization. There wasobtained a crop of crude crystal product which was pressured with 400p.s.i.g. of carbon monoxide.

filtered off. This crop was slurried in 50 ml. of l-N- sodium hydroxide,filtered ofi again, washed with water, dried, and recrystallized frompetroleum ether 03.1. 38- 63 C.) to give yellow crystals melting at 8486C. and analyzing C56.5%, H3.38%, and Fe-l8.7%. The theoretical valuesfor C H COC H Fe(CO) are C- 56.4%,H3.35%, and Fe18.8%.

EXAMPLE 3 Propionylation of butadiene ruthenium tricarbonyl Thisreaction is carried out exactly like that in Example 1 except that nonitrogen flushing is used, propionyl chloride is substituted for theacetyl chloride, and butadiene ruthenium tricarbonyl substituted for thecorresponding iron compound, both substitutions being on a mole-formolebasis. (The ruthenium compound is prepared by heating rutheniumpentacarbonyl with 1,3-butadiene in equimolar proportions, in atetrahydrofuran diluent to 150 C. for 4 hours in an autoclave in anatmosphere of nitrogen.) A yield of propionyl butadiene ruthenium'tricarbonyl much poorer than that of Example 1 is obtained from thepropionylation.

To check the effect of the nitrogen flushing, Example 1 was repeatedwithout the use of this flush. In the repetition, 35 g. of anhydrousAlCl was used, along with 14.6 g. of acetyl chloride, dissolved in 500ml. carbon tetrachloride. Forty-nine grams of the iron compound wasadded without prior dilution and the yield of acetyl butadiene irontricarbonyl, based on consumed iron compound, was 2.7%.

The lower yield thus obtained is characteristic of the results when thereaction is permitted to proceed Without flushing. The flushing action,which can be effected with any gas inert to the reaction conditions,seems to reduce by-product formation, and makes the acylated materialspractical intermediates for the production of uncombined acylbutadienes. In addition, the nitrogen, argon, carbon monoxide, hydrogen,carbon dioxide, methane, and other conventional gases, make etfectiveflushing gases.

The uncombined acyl butadienes are readily derived from the acylbutadiene metal tricarbonyls by cleavage with carbon monoxide. This isillustrated by the following example.

EXAMPLE 4 Cleavage of acetylbutadz'ene iron tricarbonyl t0 acetylbutadiene A solution of 27.5 g. (.12 mole) of acetyl butadiene irontricarbonyl (as produced in Example 1) in 800 ml. of tetrahydrofuran wascharged into an autoclave and The charge was heated to 175 C. in twohours, then held at 175 C. plus or minus 2 for one hour. A pressure dropof 80 p.s.i. was noticed during the last hour of heating. Then theautoclave was cooled to 25 C. and discharged. The resulting reactionmixture was filtered, the solvent evaporated in vacuo, and the residualconcentrated solution filtered and distilled under reduced pressureusing a short Vigreux column. A mixture of iron carbonyl and solvent wasfirst driven off and a main fraction was collected at 40-41 C. under a.pressure of 4.5 mm. Hg. The total amount of product obtained was 4.8 g.(41% of theory).

The infrared spectrum of the product showed a doublet in the 6 mu region(5.95 and 6 .0 mu). It was a mixture of l-acetyland2-acetyl-butadiene-l,3 and this mixture is easily separated by gaschromatography. Most of the mixture (over 80%) is the l-acetyl compoundwhich has a slightly higher boiling point than its 2-isomer.

The osmium compounds corresponding to the above ron and rutheniumcompounds show the same chemical behavior and can be also used forsimilar intermediates.

By reason of the inexpensive characterof the iron compounds, these arepreferred. The acylation conditions can be varied over the conventionalranges of temperaturee.g., 20 to +150 C., and pressure-e.g., below 1 mm.of mercury to several atmospheres, but it is preferred to use reactantsat temperatures low enough so that they are not gaseous, and it is mostconvenient to have the reaction take place at atmospheric pressure. Thecombination of non-gaseous reactants and atmospheric pressure makes it avery simple matter to use a gas flush as described above. DifferentFriedel-Crafts catalysts provide diiferent reaction velocities andaluminum chloride seems to be the most vigorous.

The cleavage to recover the free acylbutadienes can be carried outdirectly on the crude reaction mixture resulting from the acylation, asby carrying out the acylation in an autoclave at atmospheric pressure,and after the acylation is completed, introducing CO, sealing theautoclave and pressurizing. The CO can also be bubbled through the crudereaction mixture before the autoclave is sealed, so as to expel some ormost of the HCl remaining as acylation by-product. However, it is alsoconvenient to first separate the aqueous layer formed when hydrolyzingthe acylation mixture, and to carry out the cleavage on the organiclayer.

Cleavage takes place under carbon monoxide pressures of at least about 2gauge atmospheres and at temperatures of at least about C. Temperaturesabove 300 C. tend to cause excessive decomposition during thecarbonylation, but this can be minimized somewhat by using.

pressures of 10,000 p.s.i.g. or more.

The butadiene iron subgroup metal tricarbonyls are fairly inertchemicals notwithstanding their ready acylation. They are not alkylated,nor are they readily cleaved or otherwise decomposed by conventionalreagents other than CO. Strong acids, strong alkalis and evenultraviolet light and air do not cause any appreciable decom position atreasonably elevated temperatures. This general inertness along with thefairly ready acylation is also characteristic of these compounds whenthe butadiene is substituted by alkyl or aryl groups having up to about10 carbon atoms each as in isoprene, decadiene-4,6 and1-phenyl-butadiene-1,3. At least one of the butadiene hydrogens must beunsubstituted so that it can be replaced by the acylation. Foracyaltion, any acyl halide containing up to 20 carbon atoms can be used.Representative of such halides, aside from those of the above examples,are stearoyl bromide, alpha-naphthoyl chloride, the mixed acyl chloridesobtained by reacting tung oil fatty acids with PO1 forrnyl chloride,cinnamoyl fluoride, and p-toluene sulfonyl chloride.

At high temperatures such as 300 C. or higher, the acylated butadienemetal tricarbonyls of the present invention decompose gradually todeposit free metal in a form that makes these materials suitable for gasplating.

Obviously, many modifications and variations of the present inventionare possible in the light of the above teachings. It is, therefore, tobe understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically described.

What is claimed is:

1. A process for preparing an acylated butadiene, said processcomprising (a) reacting a butadiene iron subgroup metal tricarbonyl, inthe presence of a Friedel-Crafts catalyst, with a carboxyacyl halidehaving up to 20 carbon atoms, and wherein the radical bonded to thecarbonyl halide group in said carboxyacyl halide is selected from theclass consisting of alkyl and aryl radicals, and

(b) cleaving the acylated product thus formed with carbon monoxide at atemperature of from 100 to 300 C. and at a pressure of at least 2 gaugeatmos; pheres to produce said acylated butadiene.

- 5 2. The process of claim 1 wherein said carboxyacyl halide is acetylchloride.-

3. The process of claim 1 wherein said carboxyacyl halide is benzoylchloride.

4. A process for preparing an acylated butadiene, said processcomprising (a) reacting a butadiene iron subgroup metal tricar bonyl, inthe presence of aluminum chloride catalyst, with a carboxyacyl chloride,wherein the radical bonded to the carbonyl group in said carboxyacylchloride is selected from the class consisting of alkyl and arylradicals, and (b) cleaving the acylated product thus formed with carbonmonoxide at a temperature of from 100 to 300 C. and at a pressure of atleast 2 gauge atmospheres to produce said acylated butadiene. 5. Theprocess of claim 4 wherein said carboxyacyl chloride is acetyl chloride.

6. The process of claim 4 wherein said carboxyacyl chloride is benzoylchloride.

7. A process for preparing acetyl butadiene, said process comprising (a)reacting butadiene iron tricarbonyl in the presence of a Friedel-Craftscatalyst with acetyl chloride, and (b) cleaving the acylated productthus formed with carbon monoxide at a temperature of from 100 to 300 C.and at a pressure of at least 2 gauge atmospheres to produce said acetylbutadiene. 8. The process of claim 7 wherein said Friedel-Craftscatalyst is aluminum chloride.

No references cited.

LEON ZITVER, Primary Examiner.

D. D. HORWITZ, Assistant Examiner.

1. A PROCESS FOR PREPARING AN ACLATED BUTADIENE, SAID PROCESS COMPRISING (A) REACTING A BUTADIENE IRON SUBGROUP METAL TRICARBONYL, IN THE PRESENCE OF A FRIEDEL-CRAFTS CATALYST, WITH A CARBOXYACYL HALIDE HAVING UP TO 20 CARBON ATOMS, AND WHEREIN THE RADICAL BONDED TO THE CARBONYL HALIDE GROUP IN SAID CARBOXYACYL HALIDE IS SELECTED FROM THE CLASS CONSISTING OF ALKYL AND ARYL RADICALS, AND (B) CLEAVING THE ACYLATED PRODUCT THUS FORMED WITH CARBON MONOXIDE AT A TEMPERATURE OF FROM 100* TO 300*C. AND AT A PRESSURE OF AT LEAST 2 GAUGE ATMOSPHERES TO PRODUCE SAID ACYLATED BUTADIENE. 